1. Field of the Invention
The present invention relates to golf balls in which an urethane based resin is used in the cover.
2. Description of the Related Art
Golf balls in which an urethane resin is used in the cover have been developed. These golf balls are excellent in performances in approach and scuff resistance. These golf balls are likely to be preferred by high-level golf players. Also, the golf balls in which an urethane resin is used in the cover may be employed as balls for golf practice range (generally, may be also referred to as “range ball”). In particular, in the case of use as the ball for golf practice range, durability in repeated use and in use for a long period of time is demanded.
As described above, the golf balls having an urethane cover are excellent in the scuff resistance performance, therefore, scuffing and breakage are less likely to be caused even though they are repeatedly used in golf practice range and the like. To the contrary, the urethane resin is more likely to subject to color change by an ultraviolet ray as compared with ionomer resins. The golf balls having an urethane cover are more likely to subject to color change by use for a long period of time. Particularly, the color change causes problems in the case of the balls for golf practice range.
Techniques in which an ultraviolet ray absorbing agent is included in a cover or a paint was proposed in order to inhibit influences of the ultraviolet ray. Japanese Unexamined Patent Application Publication No. Sho 64-70086 (U.S. Pat. No. 5,156,405) discloses a golf ball in which an ultraviolet ray absorbing agent is included in a cover constituted with an ionomer resin, and in a clear paint. Japanese Unexamined Patent Application Publication No. 2000-516521 (published Japanese translation of a PCT Application) (U.S. Pat. No. 5,840,788) discloses a golf ball in which an urethane top coat includes an optical brightening agent which absorbs ultraviolet rays. Japanese Unexamined Patent Application Publication No. 2002-126132 (United States Patent Application Publication No. 2002/077197) discloses a golf ball in which the surficial part of the ball main body does not substantially include an ultraviolet ray absorbing agent but the paint layer includes an ultraviolet ray absorbing agent.